1. Field of the Invention
The present invention generally relates to a mobile robot steering method and a controlling device for a mobile robot and more particularly, to a method which allows the mobile robot to run throughout almost the entirety of a given area in a shorter period of time and a device for implementing the same.
2. Description of the Related Art
Mobile robots, including a cleaner robot, a mower robot, a plasterer robot, and an agricultural sprayer robot, are known which automatically run throughout a given area for accomplishment of an imposed task. For example, a cleaner robot, is disclosed in Japanese Patent Laid-open Publication No. HEI 5-46246 (hereinafter "JP '246"). The cleaner robot of JP '246 first runs about in a target room to be cleaned to map out a running or cleaning area through detection of the size and shape of the target room and the locations of obstacles in the room. Coordinates data, produced by the mapping, are then used for a mobile robot to clean the room while running in either a zigzag pattern or a spiral pattern in which the radius of circling is gradually decreased after every turn. The robot includes contact sensors and supersonic sensors for detecting walls around the robot to determine the robot's route. The robot also includes a distance meter for measuring the distance traveled in order to know the end of the circling motion. Another mobile robot, for running around throughout the whole area of a given floor, is disclosed in Japanese Patent Laid-open Publication No. HEI 5-257533 (hereinafter "JP '533").
Such conventional mobile robots, as shown in JP '246 and JP '533, are generally provided with a number of sensors. The outputs of the sensors are used for acquiring the data of an area to be traveled and determining the operations to be performed for running through. More particularly, the outputs of the sensors are constantly transferred to a central controlling unit, which in turn determines the controlling action for steering the robot at high accuracy on the basis of the sensor outputs. Driving actuators, such as motors, are controlled on the basis of these determinations.
When the central controlling unit handles the outputs of all of the sensors, the system of the central controlling unit should be sophisticated and the central controlling unit's processing speed will be lowered. Such a lower processing speed may retard and thus, take an averting action, when encountering an obstacle such as a wall. Also, time for mapping, teaching, and settings of relevant thresholds and initial values are required, for various kinds of controls and skills for the settings.
Accordingly, conventional mobile robots are so bulky in size, heavy in weight, and costly that the applications thereof will be limited. Examples of the limited applications are, for instance, as transporting robots and as cleaning robots in plants.
Not all robots have to run throughout the entirety of a target area at a higher accuracy, but some robots are allowed to run throughout the area with a considerable degree of accuracy. The routes and directions of these robots may not be critical. In some cases of a cleaning robot, for example, the area to be cleaned does not always have to be covered in its entirety, but rather some of the area can remain uncleaned. Depending on the requirements of some mower robots, the mower robots must produce highly neat traces of mowed area and the other mower robots are expected to perform a mowing operation only at a substantial level.